Add network-topolopy support

Add a new api about network-topolopy in openstackclient
It is the intention for OSC to collect data from existing
REST APIs

Change-Id: I23709ee906555d773c3efeb094aef50587732a1b
Related-Bug: #1586584
Implements: bp network-topology-support

Author: dongwenshuai

doc/source/specs/network-topology.rst

@@ -0,0 +1,44 @@
+================
+network topology
+================
+
+A **network topology** shows a topological graph about
+devices which connect to the specific network. Also, it
+will return availability information for each individual
+device within the network as well. One other thing to note
+is that it is the intention for OSC to collect data from
+existing REST APIs
+
+Network v2
+
+network topology list
+---------------------
+
+List network topologies
+
+.. program:: network topology list
+.. code:: bash
+
+    os network topology list
+        [--project <project>]
+
+.. option:: --project <project>
+
+    List network topologies for given project
+    (name or ID)
+
+network topology show
+---------------------
+
+Show network topology details
+
+.. program:: network topology show
+.. code:: bash
+
+    os network topology show
+        <network>
+
+.. _network_topology_show-network
+.. describe:: <network>
+
+    Show network topology for a specific network (name or ID)